Damper motor



Sept. 1-2, 1933-. c. a. KRONMILLER DAMPER MOTOR 'Filed'llarch 25, 1931 6Sheets-Sheet 1 ATTORNEY!) Sept 1933- c. e. KRONMILLER 1,926,680

bwrsamo'roii Filed'March 25, 1931 '6 Sheets-Sheet 2 ATTORNEYS P .3 c. e.KRONMILLER 1,926,680

nmrsn uowon F lled March 25, 1931 e Sheets-Sheet 3 Z INVENTOR.

A TTORNEYJ Sept- 1933- c. G. KRONMILLER, 1,926,680

DAMPER MOTOR Filed March 25. 1931 6 Sheets-Sheet I INVENTOR.

p 1933- C. G. KRONMILLER 1,926,680

DAMPER MQTOR Filed March 25, 1931 6 Sheets-Sheet 5 .6 r mwyawjhe lw h w4I ATTORNEY? VINVENTOR.

p 1933- c. s. KRONMILLER DAMPER MOTOR s Sheets-Sheet 6 Filed March 25,1931 v INVENTOR.

ATTORNEYS Patented Sept-J2, 1933 UNIT-so srA TEST-PAT ENT oFFlc-E DAMPERMOTOR earl G. Kronmiller, Elkhal't, Ind., assignor toMinneapolis-Honeywell Regulator Company,

Minneapolis, Minn ware a corporation of Dela- Application March 25,1931.- Serial No. 525,170

. and effective in operation, and adapted to be 0 easily manufacturedand installed at a moderate cost. The mechanism is equally adaptable forhot water, steam, vapor or warm air heating systems.

Another object of the invention resides in the srprovision of a controlmechanism'or system of this character which is adaptable to stoking inthat during the stoking period the draft and check doors or dampers maybe closed to prevent smoke from blowing out through the fire door andthis without impairing the capacity of the system to exercise itscontrol over the dampers following the stoking.

In one embodiment of the present invention the direct and check draftdampers are connected by cables, chains or other suitable motiontransmission means to an operating lever supported for rocking movementand acting when tipped or rocked in one direction to close the directdraft and open the check draft, when tipped in the other direction toopen the direct draft and close the check draft and when disposedintermediate its two extreme angled or tipped positions to close boththe direct and the check draft dampers. The operating lever is actuatedfrom an electric motor which may be an'induction. motor, the inductionmotor driving reduction gearing which acts through a crank pin, link andclutch to oscilclosed. This is especially desirable when stoking.'

Furthermore, the clutch is of such construction and is so organized-inthe motion transmission train that it is automatically re-engagedfollowing the stoking period, and this automatic recngagement may bemade to occur upon subsequent change of position of the room thermostator upon the lapse of a predetermined stoking period.

The operation of the electric motor is regulated by the conjointcactionof a room thermostat and an automatic cycle-maintaining switch wherere-engagement of the clutch following its throwout for stoking dependssolely on a change of position of the room thermostat. Where automaticclutch re-engagement is to be had at the expiration of a predeterminedstoking period, a

third switch is incorporated in thefmotor controlling circuit with theroom thermostat and the cycle-maintainingvswitch. The third switch iscontrolled by the clutch, the third switch being automatically closedwhen the clutch is disengaged and being automatically open when theclutch is engaged.

The cycle-maintaining switch prevents any possibility of incompletecycling. In other words, once the motor is started under the control ofthe room thermostat, the cycle-maintaining switch functions to maintainthe circuit complete independent of any changes in the position of the Iroom thermostat until the complete cycle has been carried out and theposition of the dampers has been completely changed or reversed.

Other objects and advantages reside in certain novel features of theconstruction, arrangement and combination of parts which will behereinafter more fully described and particularly pointed out in theappended claims, reference being had to the accompanying drawingsforming a part of this specification, and in which:

Figure 1 is a view in front elevation showing a I control unit embodyingthe present invention, the cover being removed and parts being brokenaway for the sake of illustration;

Figure 2 is a sectional view taken in the plane of'line 2--2 of Figure1; a v

Figure 3 is a view of the control unit inrear elevation, parts beingbroken away and shown in section and the rear cover plate being removedfor the sake of illustration;

Figure 4 is a view in horizontal section taken on line' 4-4 of Figure 1;

Figure 5 is a view in vertical section takeno line 5.5 of Figure 1;

Figure 6 is aview in section takenon line 6 -6 of Figure 2;

Figure 7 is a diagrammatic view showing the system installed on one typeof furnace;

Figure 8 is a wiring diagram showing how the switches are electricallyconnected with each other and with the motor in' one embodiment of theinvention; I H

Figure 9 is a view in front elevation showing a extreme in' er end ofthe shaft.

modified'form. of the invention, the front cover plate being removed;

Figure 10 is a view in section taken on line 10-10 of Figure 9;

Figure 11 is a fragmentary sectional view'taken on line 11-11 of Figure10;

Figure 12 is a view in rear elevation of the device shown in Figures 9,10, and 11; and

Figure 13 is a wiring diagram of the form of the invention shown inFigures 10 to 12.

Referring to Figure 7, the numeral 1 designates generally a furnacehaving a direct draft damper 2 and a check draft damper 3. .A cable 4con-- nects at one end with the direct draft damper 2 and after passingover guide pulleys 5 is secured to one end of an operating leverdesignated generally at 6. Similarly, a cable 7 has one end connected tothe check draft damper 3' and after passing overpulleys 8 is connectedto the op- 'or partition 13 of the casing (see Figure 2).

The power for oscillating the operating lever is supplied by an electricmotor 15, which may be a low voltage squirrel cage induction motor. The

rotor shaft of the motor 15 carries a pinion 16- which drives areduction gear train designated as a whole at 17. The reduction geartrain 17 actuates a. driving gear wheel 18, which is provided with acrank pin 19. "The crank pin 19 is pivotally connected to one end of alink 20, and the opposite end of this'link 20 is pivotally connected asat 21 to a driving member in the form of a clutch plate 22 alsosupportedfhrrotation on thebushing 11, as may be seeniiigFigure 2. Oneend of this bushing 11 is flanged as at 23 and on the opposite end a nut24 is threaded to secure the bushing in position and maintain theoperatinglever 6 andclutch plate 22- on the bushing and against axialalthough free for rotary movement. Coacting with the clutch plate 22 isa driven clutch member in the form of I a clutch bar 25, the endportions of which have In the engaged position of the clutch the pins 26project through clutch pins 26 secured thereto.

openings 2'7 in .the driving clutch plate 22 and also through openings28 in the enlarged portion 6' of the operating lever (see Figure 4). Thecentral portion of the driven clutch bar is formed with an opening 29 ofnon-circular form which is snugly 'fitted on a correspondingly formedportion 29' of a shaft 31 and is held in position thereon and thuseffectively fixed to shaft 31 by means'of a nut 36 threaded on the Theshaft 31 is fitted fo rotary and sliding motion in the bushing 11 andprojects well beyond the front end of the bushing and extends through'an insulating panel 32 suitably supported in the housing and alsoextends through the cover. 33 constituting the forward part of thehousing, the extreme front end of the shaft 31 terminating in a knob 34.A spring 35 encircles a portion of the shaft 31 and is under sufficientcompression to iseaceo ways electrically connected and so function as asingle conductor. The binding post 43 is connected by a wire 46 with abinding post designated at W,; The binding post W is the conventionalso-called white binding post or terminal and is disposed between bindingposts R and B,

which are the conventional binding posts of red and blue, respectively.The binding post W connects by a wire 47 (see Figure 8) with the movableblade contact 48 of a conventional room thermostat or thermostaticswitch designated generally at 49. The binding posts R and B connect bywires 50 and 51 with the contacts R and B of the thermostatic switch.Electrically connected with the binding posts R, W and B are thecontacts R W and B of a cycle-maintaining switch. Slidably across thesecontacts R W and B so as to be successively engageable therewith, is amovable contact 52. This' movable contact 52 may be in the form of abutton 53 carried by an insulating arm 54 constrained to rotate with theshaft 31 and urged toward the contacts R W and B by a spring 54 (seeFigures 2 and 4). The movable contact 52 is electrically connected toone side of the motor 15 by. wires 55 and 56.

The structure as thus far described is a-co'mplete and operative unitand may be used to advantage under many circumstances. Withthisstructure when the fire is to be stoked the knob 34 is pressedinwardly. This moves the clutch bar 25 and its pins 26 rearwardly anddisenga es them from the openings 28 of the 'operating lever. Theoperating lever is then moved to'a horizontal position; In this positionboth the direct draft damperand the check draft damper change itsposition the motor will be started up.

For example, if the operating }lever had occupied the position shown infull lines in Figure 1 just pr'ior to the shifting thereof to horizontalposition) then the check draft damper would have been closed and thedirect draft damper opened. This would mean, of course, that the roomthermostat had had its movable blade contact 48 engaged with contact Rand that acycle of operations had been completed the contact 52 of thecycle-maintaining switch having moved down into engagement with contactB and having thereby interrupted the motor circuit, assuming, of course,that thev contact 48 of the room thermostat still remains engaged withthe contact R If now, after disengagement of the clutch and manualshifting of the lever 6 to horizontal position, the blade 48 moves overinto engagement with the -contact B the room thermostat having beensatisfied, then a circuit will be completed through the motor, for thecurrent will flow through the wire 41, .binding -post.43, wires 46 and47, contacts 48 and B wire 51, contact 13 contact 52 and wires 55 to 56to one sideof the motor 15 and thence from the other side of the motorback through wire 45 to binding post 44 and through the wire 42 to theother side of the transformer. The motor starting up will act throughthe reduction gear to drive the gear wheel 18 and its I crank pin 19.This will move the link 20 and con- 5 'sequently the plate 22, pins 26and bar until the pins again come into registry with the openings 28 inthe lever 6. When this registration is "brought about the spring causesthe pins 26 to snap back in the position shown in Figure 4,.therebyestablishing a driving connection between the motor and the operatinglever and also between the motor and the movable contact of thecyclemaintaining switch. The operation of the motor will now continueand the lever will be shifted to the inclined position shown in dot anddash lines in Figure 3, and the contact 52 will be shifted up intoengagement-with the contact R whereupon the motor circuit will bebroken. The motor, however, remains ,under' the full 0 control of theroomthermostat and will automatically function-to rock the operatinglever to one position or the other, depending upon the condition of theroom thermostat.

In some instances it maybe desirable to have the motor operateindependently of the room thermostat during the stoking period and afterthe operating lever has been shifted to horizontal position and yet sooperate that the clutch will not be engaged until after sufficient timehas 0 elapsed to allow for a full stoking period. It will be rememberedthat one side of the transformer is directly connected with one side ofthe motor. A direct'connection or anelectrical connection independent ofthe room thermostat may 35 also be provided'between the other side ofthe transformer and the motor, this second direct connection being madeand broken under the control of a switch which may be convenientlyinterlocked with or controlled in its operation by the clutch, so thatwhen'th'e clutch is thrown out the switch will be closed and when theclutch is thrown in the switch will be opened. Further, a second set ofreduction gearing may be provided between, the motor and may be 5operatively'interposed between the first set of reduction gearing andthe driving gear when the clutch is thrown out or disengaged so that themotion transmitted tothe driving gear and v consequently to the clutchplate, clutch bar and clutch pins will be somewhat slower wherebysufflcient time will be required for the clutch pins to again come intoregistry with their cooperating openings in the operating lever, toinsure an adequate stoking period. Here again the shifting of the secondset of gearing into and out of operative position may be convenientlycontrolled from the operating means for the clutch whereby whenthe-clutch is thrown out the second set of gearing will be thrown in andvice versa. 1 i

' Referring now to Figures 1, 4 and 8, it will be-seen that the bindinpost 43 may be conneeted by wire 60 with a fixed contact 61 of .whatmaybe termed a stoking switch. Cooperable with the fixed contact 61 is amovable contact 62 which may be of the shape shown in Figure 4, fastenedby rivet 63 to the insulating panel 32 and biased by its inherentresiliency to disengaged position. The movable contact- 62 has its freeend of arcuate form as shown at l5 arm 52 and which is threaded into theshaft 31 as clearly. shown in Figure 4. The pin 65 thus servestoconstrain the roller to moye with the shaft 31 and also function toconstrain the arm 52 to rotate with the shaft 31. As will be seen fromFigure 4 this arm 52 is held against motion in the direction of the axisof the shaft 31 by virtue of its abutting panel 32 at one side and itsengagement with the spring 35 on the other side. The movable contact 62of the stoking switch is electrically connected by rivet 63 with thewire 67 electrically connected to wire 56 leading to one side of themotor 15. c

From this it will be seen that whenever the shaft 31 is pressed inwardlythe contact 62 will 7 be flexed into engagement with thecontaet 61 andthe motor circuit will be completed independently of the roomthermostat. ,However, when the shaft 31 is in its outermost position.the contact 62 automatically disengages from the contact 61 and leavesthe motor circuit \underflthe control of the room thermostat.

To constrain the contact 62 to movement toward and away from the contact61 aguide pin 68 is secured to the panel 32 and 'projects outwardlytherefrom and through a guide slot 69 in the .contact 62. a w

Referring now to Figures 2 and 5, it will be seen that the gear train 17drives the driving gear wheel 18 through a pinion 70 mounted on theshaft 7.1 actuated from the gear trainl'l and directly meshing with thegear wheel 18. If desirable, this pinion 70 may be splined on, the shaft71, that is to say, it may be so interconnected with the shaft as to beconstrained to rotate therewith and yet free to slide along the shaft.By so mounting the pinion 70 it may be selectively meshed with the gear18 or may be used to drive a large gear wheel '72 fixed to the hubextension of a pinion 73 mounted for rotantion on the short stud shaft74 and also meshed with the gear wheel 18. When the pinion 70 is shiftedinto engagement with the large gear wheel '72, the gear wheel 18 isdriven'at astill slower speed, since the gear wheel 72 and the pinion 73constitute a second set 01' reduction The shifting of the pinion '70 maybe controlled by a shifting lever '75 having its lower end fulcrumed asat ,76 on a supporting stud'l'l 125 secured to the partition 13 andhaving its upper end of forked formation and interfitted with an annulargroove '78 formed in an extension of the hub of the pinion '70. Theintermediate portion of the shifting lever "IS-may be apertured as at 79and provided with lugs 80 projecting into the aperture and confinedbetween the clutch bar 25 and the nut or head 30 secured on the adjacentend of the shaft 31. With this arrangement the shaft 31 may rotateindependently of the lever 75. However, when the shaft 31 is pressedwardly the lever '75 is shifted from the position shown in full lines inFigures 2 to the position shown in dotted lines in the same figure, withI the result that the pinion 70 is disengaged from 140 the gearwheel 18and meshed or engaged with the gear wheel '72, I When the shaft 31 movesback to its normal position it carries the lever '15 with it andconsequently the pinion '70 'is' moved back into mesh with the gearwheel 48'.

The stoking period may also be prolonged'for a desired length of timebyhaving the stoking switch operate through a delayed action relay incompleting the motor circuit. In other words, when the knob is pressedin to disengage the clutch and permit the operatinglever to be thebi-metallic element is cold it coacts with V pressed inwardly thecontact 62 of the stoking the contact which incorporates the roomthermostat in the system as the dominant control element, whereas whenthe bi-metallic, element is heated it coacts with the contact soarranged in the system as to complete the motor circuit independently ofthe room thermostat.

Referring now to Figures 9 to 13, inclusive, it will be seen that thisembodiment of the invention is identical with that hereinabovedescribed, except that it varies slightly the position of the drivinggear wheel 18, omits the second set of gearing, the shifting means forthrowing the sec-- 0nd set ,of gearing into and out of operation andintroduces the delayed action relay. As in the other embodiment, themotor 15 drives the reduction gear train 17, which actuates the drivinggear wheel 18. The driving gear wheel 18 acts through the crank pin 19and link 20 to operate the clutch plate 22. The clutch plate 22 isoperatively associated with the clutch bar 25, clutch pins 26 and withthe operating lever 6 as in the other form of the invention. The clutchis thrown in and out by the shaft 31 as before and the shaft 31 hasassociated therewith the cycle-maintaining switch, including theinsulating arm 54, movable contact 52 and fixed contacts R, W and B Thestoking switch also comprises, as before, the contacts 61 and 62, theroller 64 and associated parts.

Referring now to Figure 13, it will be seen that the room thermostat orthermostatic switch 49 is connected to the binding posts R, W and B asbefore, and further, that the transformer, 40 is connected up to thebinding posts 43 and 44 as before. The binding post 48. is electricallyconnected by wire 46 with a binding post 85. The binding post connectsby a. wire 86 with one side of the motor M and by a wire 87 with oneterminal of a resistor or electric heating element 88. The otherterminal of the heating element 88 connects by a wire 89 with thecontact 61 of the staking switch. The contact 62 of the stoking switchconnects by a wire 90 with the binding post 44. Wire 46 also connectsbinding post 44 with contact W which is at all times electricallyconnected with binding post W. Anextension 90' of the wire 90 connectsbinding post 44 with the contact 91 of a thermostatic or heat controlledswitch T. Opposite the contact 91 is a second fixed contact 92 connectedby wire 93 with the movable contact 52 of the cycle-maintaining switch.The thermostatic switch T also includes a bi-metallic or heat responsivecontact member 94, the free end of which is engageable with the fixedcontacts 91 or 92 and the nxed end of which is fastened to and insulatedfrom a supporting bracket 95 and is electrically connected by wires 96to one side of the motor.

With this organization, when'the knob 34 is switch is'engaged with thecontact 61. This com-- 1 tes thecircuit through; the resistor 88, theentflowing from binding post 44 through wir o," contacts 62 and 61, wire89, resistor 88,

Laaaeec wire 87, binding post 85, and wire 46 back to the binding post43. At this time the bi-metallic element 94 is engaged with the contact92 and the motor circuit can only be completed through the roomthermostat. However, as-the resistor 88 heats up the bi-metallicelement, the bi-metallic element flexes until its free end is disengagedfrom the contact 92 and engaged with contact The disengagement of thebi-metallic element 94 from the contact 92 makes it impossible tocomplete the motor circuit through the room thermostat, and theengagement of this element 94 with the contact 91 completes the motorcircuit independently of the room thermostat, since the current nowflows from the binding post 44 through wires 90 and 90' to contact a 91,thence through bi-metallic element 94 and wires 96 to one side of themotor. Leaving the other side of the motor the current flows throughwire 86, binding post 85, and wire 46 back to binding post 43. Thiscondition obtains and the motor isrunning until the clutch isre-engaged, at which time the spring 35 shifts the shaft 31 outwardly,thereby opening the stoking switch and interrupting the flow of currentto the heating element 88. The heating element 88 and bimetallic element94 cool ed with the result that the bi-metallic element disengagescontact '91 and engages contact 92, thereby throwing the motor backunder the control ofthe room thermostat.

If desired, a .mercury switch 100 of the type operated by tilting may besupported in a carrim or bracket 101 secured to the shaft 31 and asillustrated in Figure 8 the mercury switch may be incorporated in thecircuit of a furnace fan motor 102. As is well known, these furnace fansare used to force the circulation of air on warm air heating systems.

In all embodiments of the invention a simple, compact and reliable typeof rotary electric motor may be employed and functions through thegearing and the crank, link and clutch mechanism to drive or actuate theoperating lever for the dampers in .an effective and reliable manner.The clutch is so organized with the oper-- ating lever thatdisengagement of the clutch does not place the lever or the chainsconnected and of very compact construction and is 'sus- I ceptible ofbeing manufactured and installed at a very moderate cost.

The invention claimed is:

l. A control system for a damper comprising an operating lever connectedto the damper, a motor, a room thermostat controlling the operation ofthe motor, motion transmission means between the motor and the leverincluding a manually releasable clutch to provide for adjustment of thelever independently of the motor for stoking and means for energizingthe motor independently or the room thermostat and including a normally'open stoking switch interconnected with the manually operable clutchwhereby said normally open switch is closed when the clutch isdisengaged and is opened when the clutch is engaged, and a delayedaction relay incorporated in the motor circuit and controlled by thestoking switch to complete the motor circuit independently of the roomthermostat when the stoking switch is closed.

2. A control system for a damper comprising an operating lever connectedto the damper, a motor, a room thermostat controlling the operationofthe-motor, motion transrfiition means between the motor and the leverincluding a manually releasable clutch to provide for adjustment of thelever independently of the motor for stoking, and means for energizingthe motor independently of the room thermostat and including a normallyopen-stoking switch interconnected with the manually operable clutchwhereby said normally open switch is closed when the clutch isdisengaged and is opened when the clutch is engaged, and a delayedaction relay incorporated in the motor circuit and controlled by thestokingswitch to complete'the motor circuit ,independently of the roomthermostat when the stoking switch is closed, said delayed action relayincluding a thermostat switch having a bi-metallic element, fixedcontacts cooperable with said bimetallic element and connected in themotor circuit to provide forthe completion of the circuit through theroom thermostat whenthe bi-metallic element is cold and for completionof the motor circuit independently of the room thermostat when thebi-metallic element is heated and an electric heating element incooperative relation to the bi-metallic element and interconnected withand energized under the control'of the stoking switch.

3. A control system for dampers comprising an operating lever connectedto said dampers, a

motor, a room thermostat controlling the operation of the motor, a setof reduction gearing actuated by the motor, a rotatable driving elementactuated from the gear train, motion transmission means actuatedfromsaidrotatable driving'element and connected to the operating'lever forreversely' operating the same upon rota- "tion of said driving element,said motion transoperating lever connected to he dampers, a motor, areduction gear train actuated by the motor and having a shiftablepinion, a driving gear element, a second reduction gear train connectedwith the driving gear element, said shiftable pinion being adapted todirectly drive the driving gear element or to drive the second reductiongear train, motion transmission means between the driving gear elementand the operating lever and including a manually releasable clutch, aroom thermostat controlling the operation of the motor, 'means operatedwhen '.the clutch is thrown out to complete the motor circuitindependently of the room thermostat and means operated when the clutchis thrown out ,to-engage said shiftable pinion with the second reductiongear set.

5. A control system for a damper comprising an ,operatinglever connectedto'the damper, a motor,

motion-,transmiss'ion meansf actuated by the motor and including adriving gear wheel having a I; crank pin, a link actuated from thecrank. pin,

clutchihaving a member connected to the link having openings with whichthe pins are v hen-in registry therewith, means to snap intosaldopenings, ns ior'disenmin the having pins ,actua'tedby said member,saidpins from said openings whereby to permit the lever, to be shiftedindependently of the motor,

, a reduction gear train controlled. by the manually "operable means andshifted into operative position between the motor and the driving gearwheel when the clutch is disengaged.

. 6. A control system for a damper comprising an operating leverconnected to the damper, a motor, motion transmission means actuatedbythe m o-- tor and including a drive gear wheel having a crank pin, alink actuated from the crank\pin, a clutch driving member pivotallyconnected to the link, a cooperable clutch member having clutch pins,said clutch driving member and said lever having openings with whichsaid pins are engagaeable when in registry. therewith, a shaft fixed tosaid cooperable clutch member and shiftable to disengage. the pins fromthe openmgsof the lever and means for biasing the pins to snap into saidopenings.

7. In a control apparatus for regulating afheating plant, a heataccelerating and fretarding means, a thermostat subject to .thetemperature to be controlled,.the thermostat n'ormally controlling.thesaid means, a manually operable mechanism for operating said meansindepend-t ently of saidthermostat, a temperature responsive deviceadapted to restore control to the room thermostat when heated to apredetermined degree, heating means therefor, a source of power, aswitch andwires interconnectingv the source of power, heating means andswitch, the parts being arranged so that manual operation ofsaidmechanismtcloses said switch. v, Q I f v 8. A control system for adamper comprising an operating lever connected vto the damper, a rotarymotor, motion transmission-means actuated by the motor and including adrive gear wheel having a crank pin, a link actuatedffr'om the crankpin', a clutch driving member pivotally connected to the link, acooperable clutchfmember having clutch pins, said clutch driving memberand said lever having openings withwhich said pins are engageable whenin registry therewith, a. shaft fixed to said cooperable clutch memberand shiftable to disengage the pins from the openings of the lever,means for biasing the pins to snap into said openings, said lever beingshiftable angularly with respect to the pins when the pinsare disengagedfrom its openings, whereby the clutch is held disengaged until the pinsare again brought into registration with the openings of the leverunder-the action of the motor, and means for delaying the action of themotor--in*efiecting such registration until after the lapse of apredetermined stoking period.

9. A control system for a? damper comprising an operating leverconnected to the damper, a rotary motor, motion transmission means actu:ated by the motor and including a drive gear wheel having a. crank pin,a link actuated from the crank pin, a clutch driving member pivotallyconnected to the link, a cooperable clutch member having clutch pins,said clutch driving member and-said leverhavin'g openings'withwhich saidpins are engageable when in registry therewith, a shaft fixed to saidcooperable clutch member and shiftable to disengageithe pins from theopenings of the lever, and means fonbiasing the pins to-snap into saidopenings, said-lever being shiftable angularly with respect tothe pinswhen the pins are disengaged from its openings, whereby the clutch isheld disengaged until the pins are again. brought into registration withthe openings of the lever under the action of the motor.

10. A control system for a damper comprising anoperating lever connectedto the damper, a rotary motor, gearing actuated by the rotary motor,motion transmission means actuated by the gearing for rocking the leverfirst in one direction and then in the other upon continuous operationof the motor in one direction, said motion transmission means includinga clutch for establishing a driving connection between the motiontransmission means and the lever, manually operable means for shiftingthe clutch to disengaged position wherein the driving connection betweenthe motion transmission means'and the lever is broken, said lever beingshiftable out of lished.

11. A control system for a damper comprising an operating leverconnected to the damper, a rotary motor, gearing actuated by the rotarymotor, motion transmission means actuated by the gearing for rocking thelever first in one direction and then in the other upon continuousoperation of the motor in one direction, said motion transmission meansincluding a clutch for establishing a driving connection between themotion transmission means and the lever, manually operable means forshifting the clutch to disengazed position wherein the drivingconnection ripeness the predetermined angular relation between the leverand the clutch has been re-established, and means for efiectingoperation of the motor upon movement 01 the clutch to disengagedposition whereby the motor re -establishes said predetermined angularrelation between said clutch and said lever.

12. A control system for a damper comprising an operating leverconnected to the damper, a rotary motor, gearing actuated by the rotarymotor, motion transmission means actuated by the gearing for rocking thelever first in one direction and then in the other upon continuousoperation of the motor in one direction, said motion transmission meansincluding a clutch for establishing a driving connection between themotion transmission means and the'lever, manually operable means torshifting the clutch to disengaged position wherein the drivingconnection between the motion transmission means and the lever isbroken, /said lever being shiftable out 01' predetermined angularrelation with said clutch when the clutch is disengaged, yieldable meansfor urging the clutch to engaged position, said clutch being movable toengaged position under the influence of said yieldable means only whenthe predetermined angular relation between the lever and the clutch hasbeen re-established. means for eflecting operation or the motor uponmovement of the clutch to disengaged position whereby the motorre-establishes said predetermined angular relation between said clutchand said lever, and means for prolonging the time required for the motorto re-establish the predetermined angular relation of and consequentlythe driving connection between said clutch and said lever.

CARL G. KRONMILLER.

